After winning the 74th Hunger Games in the previous novel, Katniss and Peeta return home to District 12, the poorest sector in the country of Panem. Katniss and Peeta are preparing to embark on a "Victory Tour" of Panem, but have rarely spoken since they won the Games and Peeta realized that Katniss' emotions towards him were exaggerated at their mentor Haymitch Abernathy's request. Katniss struggles to understand her feelings about Peeta, and also Gale, who kissed Katniss upon her return to District 12. The day Katniss is due to leave, the Capitol's President Snow arrives at Katniss' home and sternly warns her that she needs to convince Panem's citizens that she and Peeta are truly in love; their actions in the Games have sparked unrest across the districts and many believe their attempted suicide was actually a defiant act against the Capitol rather than sacrificing themselves for love. Snow indirectly threatens both Gale's and Katniss' families.
The Victory Tour's first stop is District 11, home to Katniss' friend and ally in the Hunger Games, Rue, before she died. During the ceremony, Katniss and Peeta deliver quick speeches to District 11, thanking its people for their tributes. Peeta offers to donate a portion of his Victory winnings to Rue's family, and also Thresh's, the other fallen District 11 tribute. When the speeches conclude, an old man whistles the tune that Rue used in the Hunger Games arena to signal Katniss she was safe. The song prompts everyone to salute Katniss with the same gesture she used to bid farewell to Rue. However, the old man is shot dead, and the Capitol refuses to let the pair make any more personal speeches during the the tour. Katniss and Peeta then travel to all twelve districts and the Capitol. Katniss urges Peeta to emphasise their supposed love and, during a televised interview, Peeta proposes to Katniss. The Capitol responds by planning an elaborate wedding ceremony for the two. Despite this, Katniss learns that their attempts to subdue rebellion in the districts and convincing Snow they are in love have failed. Back in District 12, Katniss accidentally sees a secret TV report showing a violent uprising in District 8, where many citizens are killed by Peacekeepers, Panem's security force. After this event, District's 12's security is massively tightened, and the current Peacekeepers are replaced with stricter ones. Gale is whipped by the new Head Peacekeeper for hunting, and the fence surrounding District 12 is now constantly electrified, effectively barring Katniss from escape or hunting. Katniss had made it into the woods where she encountered two runaways from District 8. She offered them food, and they have a theory that District 13 was not wiped out by the Capitol and that its residents have gone underground. She is able to get over the electrified fence and back into the district, but is slightly injured.
Later, Cinna and his stylists arrive to help Katniss prepare for her bridal shoot. The stylists tell her about supply shortages across the Capitol, leading Katniss to suspect that rebellions and uprisings are spreading across Panem. President Snow announces that, for the 75th Hunger Games, as part of the "Quarter Quell", a special edition of the Games every quarter-century, tributes will be reaped from a pool of all living Victors of past Hunger Games. Being the only living female victor from District 12, Katniss is chosen for the Quarter Quell by default. When Haymitch is chosen as male tribute, Peeta volunteers in his place to protect Katniss. Desperate to prepare, the trio begin training and studying the winning tactics of past victors.
After arriving at the Capitol, Katniss and Peeta look for potential allies among the other tributes. Katniss meets Finnick Odair, a 24-year-old man who successfully survived the Games at age 14, and Mags, Finnick's 80-year-old mentor, both from District 4. She also meets Beetee and Wiress, older tributes from District 3 who are said to be "exceptionally smart" and adept at working with electronics. Beetee and Wiress tell Katniss that the Capitol leaves the control panels for their force fields vulnerable in plain sight. During the training display to the Gamemakers, Peeta and Katniss show their defiance of the Capitol and having to return to the Games; Peeta paints Rue's death and Katniss hangs a dummy, labeling it, "Seneca Crane," in reference to the previous Gamemaker who was executed. During the interviews, Katniss wears a bridal gown that, when she twirls, harmlessly burns away to reveal a mockingjay costume. Cinna planned this as an act of defiance. Before the Games begin, Katniss is forced to watch in horror as several Peacemakers beat Cinna and drag him away.
The new Games arena is a beach and jungle terrain with the Cornucopia located on a small island in the center of a miniature sea. The arena resembles an analog clock with one lethal event occurring every hour on a twelve hour cycle. When the Games start, Katniss and Peeta form an impromptu alliance with Finnick and Mags. They search for the arena's perimeter, but Peeta runs into the force field at the edge, stopping his heart. Finnick revives him using CPR, though Peeta is weakened from the incident. At midnight, lightning strikes a nearby tree, and the next hour the Gamemakers release a poisonous fog in the group's location. The toxic fog causes nerve failure and muscle spasms which inhibits their running while Katniss tries to carry Mags and Finnick carries Peeta. Mags sacrifices herself when Katniss can no longer carry her, allowing the other three to escape. After Mags' death, the group is attacked by mutated monkeys, but all three survive, thanks to the female tribute from District 6 sacrificing herself to save Peeta. Katniss, Peeta, and Finnick join forces with Johanna Mason, a sarcastic and often cruel victor from District 7, an injured Beetee, and Wiress, who is in shock and repeatedly mumbles "tick tock." From Wiress' words, Katniss realizes that the arena is arranged like a clock, with the Gamemakers' disasters occurring on a timed chart, signaled by the lightning at 12 o'clock.
While gathered at the central Cornucopia, the Careers attack the group, killing Wiress, and a battle ensues until the Gamemakers cut it short by rapidly shifting the terrain and disorienting the Tributes. Beetee devises a plan to harness the arena's lightning to supposedly electrocute the rest of the Career tributes when they venture near the water. At night, the group splits to prepare for the plan, but is attacked separately by the remaining tributes. Katniss is knocked out and has her tracker removed by Johanna. Johanna then leads the two remaining careers away from Katniss. An injured Katniss comes across Beetee, holding a knife tied to the wire and appearing to have planned to direct the knife into the force field. Katniss directs the lightning at the force field's control panel with an arrow tied to the wire, destroying the force field and temporarily paralyzing her. When she awakens, Katniss discovers she is being transported to District 13: a place widely believed to no longer exist. She is joined by Finnick, Beetee, and Haymitch, but learns that the Capitol has captured Peeta and Johanna. Katniss is told that there had been a plan among most of the tributes, Haymitch, and Head Gamemaker Plutarch, who secretly opposes the Capitol, to break her and Peeta out of the arena. Katniss' image has become the symbol of the rebellion, which has spread to almost every district during the Games, and all the victors in the alliance were determined to sacrifice themselvs to keep Katniss alive. Finally, Katniss' best friend, Gale, informs her that, although he escaped with her family, District 12 has been bombed and destroyed.